The present invention relates generally to method for repositioning or repairing holes in metal substrates such as metal components used in jet engines and the like, and more particularly to method for repositioning or repairing holes such metal substrates using a physically deformable metal insert.
Many metal components such as nozzle supports and rotor or compressor disks used in jet engines require holes to be drilled in the component so that other components can bolted on or otherwise attached thereto. For example, U.S. Pat. No. 4,953,777 (Griffith et al), issued Sep. 4, 1990, shows fan rotor assemblies used in jet engines where the fan blades are mounted on a rotatable disk. The fan blades can have one or more tangs by which the blades are attached in spaced relation around the periphery of the disk. In one such embodiment, the blade has three tangs, each having a hole therein aligned along the same axis. The blade is mounted to the disk, the center tang entering a peripheral annular space of the disk, with the two outer tangs extending along the outside surface of each side of the disk which also has holes that line up with the holes of the tangs. A retaining pin is then passed through the holes in the disk and the aligned holes of the tangs to attach each of the blades to the periphery of the disk.
Another example of an engine component with drilled holes is illustrated in U.S. Pat. No. 5,111,570 (Baumgarten et al), issued May 12, 1992. In FIG. 1 of this patent is shown an integrally bladed compressor disk 1 having a plurality of bolt holes 2 located on spaced arrangement around the circumference of flange 3. Other engine components are joined to this compressor disk by bolting these components onto flange 3 using bolt holes 2.
When holes are drilled or otherwise formed in such metal components, one or more of the holes can mislocated, misaligned, misdrilled, or damaged during assembly of the components or during use. For example, the holes formed in these components can be subjected to stress during use and wear away or deform. This can lead to removal, discarding or scrapping of the component where the mislocated, misaligned, misdrilled, or damaged hole is located. This can be very expensive, especially in the case of certain components such as rotor or compressor disks used in jet engines. For example, in the case of integrally bladed rotors, substantial expense has been incurred prior to joining the components to each other. Accordingly, as the value of the individual assembly increases, the margin of error in machining and joining these components together becomes even more critical.
In the past, such mislocated, misaligned, misdrilled, or damaged holes were sometimes repaired by welding. However, welding and subsequent heat treatment to reposition or repair the hole can cause undesired distortion of the component, as well as a reduction the metal fatigue capability of a component that can be subjected to high temperatures and stresses during use, as is typically the case of the jet engine components. In the case of certain metal alloys such as high volume fraction gamma prime nickel-base superalloys, components made from such alloys are not weldable due to strain age cracking.
Another method for repositioning or repairing such holes is described in U.S. Pat. No. 4,953,777. In the method of this patent, as particularly shown in FIGS. 2A-C and 3, hole 19 to be repaired is machined to a diameter sufficient to remove the damaged portion and to provide a new enlarged hole with a smooth finish. A metal bushing 20 having a composition compatible with the metal component being repaired is then inserted into this enlarged hole 19. The outer diameter of bushing 19 is machined to provide a close fit with the enlarged hole 19. Following insertion of bushing 20 into the enlarged hole 19, metal mandrel 21 is inserted into the bushing opening and the resulting assembly heated to cause diffusion bonding of bushing to the component 17. The assembly is then cooled and mandrel 21 is removed to provide the new hole formed by the opening in bushing 20. Again, like welding, diffusion bonding of the bushing according to this patent can cause undesired distortion of the component.
A variation of the method involved in U.S. Pat. No. 4,953,777 is to use a threaded or flanged bushing to reposition or repair the hole. In this situation, the threaded or flanged bushing is held within the enlarged hole by frictional forces. However, the use of threaded or flanged bushing may not be possible those situations where the hole to be repositioned or repaired is relatively small in diameter, where the area where the hole to be repositioned or repaired is relatively small or both. Also, threaded or flanged bushings are frequently held in place by green tack welds that have a tendency to crack over time and allow the bushing to migrate axially within the hole.
Another method for repositioning or repairing such holes is described in U.S. Pat. No. 5,111,570. In the method of this patent, as particularly shown in FIGS. 2-4, an enlarged hole indicated by 5 is formed such as by drilling in flange 3. Repair plug, 6 is positioned in enlarged hole 5 and then a forge joining pressure is applied from both ends of the plug, such by upper and lower punches 9 and 10 that are shaped and positioned to promote uniform heating and deformation of plug 6. While this force is applied by punches 9 and 10, the interface between plug 6 and the wall of enlarged hole 5 is locally heated. After the forge joining step, excess protrusion material 11 located on both sides of flange 3 can be machined away, leaving, a smooth flange surface that can be redrilled to provide a new hole 13 of selected position and diameter as shown in FIG. 7. Again, like welding and diffusion bonding, heating of the plug can cause undesired distortion of the component. In addition, like a threaded or flanged bushing, plug 6 can be subject to axial movement within enlarged hole 5 over time after the removal of the excess material 11.
Accordingly, it would desirable, therefore, to provide a method for repositioning or repairing mislocated, misaligned, misdrilled, or damaged holes in metal components that can be achieved without the use of an insert other than a threaded or flanged bushing, does not require heating of the component or insert used in the repositioning or repair of the hole, and which avoids or minimizes axial migration of the insert used to reposition or repair the hole.
The present invention relates to a method for repositioning or repairing a hole in a metal substrate having a first and second surface where the hole extends through the metal substrate from the first surface to the second surface of the substrate. In this method, the diameter of the hole is enlarged through the metal substrate from the first to the second surface to form an enlarged hole. A first recess having a wall with at least a portion of its diameter larger than the diameter of the enlarged hole is formed in one surface of the metal substrate at one end of the enlarged bole. A second recess having a wall with at least a portion of its diameter larger than the diameter of the enlarged hole is formed in the other surface of the metal substrate at the other end of the enlarged hole. A physically deformable metal insert having a head portion and body portion is provided and is inserted through one recess at one end of the enlarged hole so that the body portion extends at least partially within the enlarged hole. The head portion of the insert has an end with a diameter larger than the diameter of the enlarged hole, and is sized and configured so as to be capable of frictionally engaging the wall of one of the recesses. The body portion of the insert has an end, a diameter sized to permit it to be inserted at least partially within the enlarged hole and a length such that the end of the body portion is capable of extending at least to the other recess. After insertion, the head and body portions of the insert are then subjected to physical forces so as to cause the head portion of the insert to be deformed and frictionally engage the wall of the one recess, so as to cause the body portion of the insert to be deformed and frictionally engage the enlarged hole and so as to cause the end of the body portion to be deformed and frictionally engage the wall of the other recess so that insert becomes substantially axially fixed within the enlarged hole. A new, repositioned or repaired hole having a diameter smaller than that of the enlarged hole can then be formed in the fixed insert that extends axially therethrough from the end of the head portion to the end of the body portion.
The method of the present allows mislocated, misaligned, misdrilled, or damaged holes in the metal substrate to be repaired or repositioned without the use of heat treatment that can cause distortion or degradation of metal substrate. The use of the deformable metal insert having the head portion with a diameter sized to frictionally engage the wall of one of the recesses formed in one surface of the metal substrate, along with the end of the body portion of the insert that is capable of being deformed to frictionally engage the wall of the other recess formed in the other surface of the substrate, allows the insert to be substantially axially fixed within the enlarged hole. As a result, the insert tends not to migrate axially within the enlarged hole, even over time.